Method for distributed power harvesting using DC power sources

• US 8,013,472 B2
• Filed: 12/04/2007
• Issued: 09/06/2011
• Est. Priority Date: 12/06/2006
• Status: Active Grant

• Current Assignee: Solaredge Limited, Solaredge Technologies Incorporated
• Original Assignee: Solaredge Limited
• Inventors: Galin, Yoav, Fishelov, Amir, Adest, Meir, Sella, Guy, Handelsman, Lior
• Primary Examiner(s): Fureman; Jared J
• Assistant Examiner(s): AMAYA, CARLOS DAVID
• Application Number:
  US11/950,307
• Publication Number:
  US 20080150366A1
• Time in Patent Office: 1,372 Days
• Field of Search: 307/77, 307/82
• US Class Current: 307/77
• CPC Class Codes: H02J 2300/26 involving maximum power point tracking control for photovoltaic sources maximum power point systems in particular G05F1/67
• CPC Class Codes: H02J 2300/30 The power source being a fuel cell
• CPC Class Codes: H02J 3/18 Arrangements for adjusting, eliminating or compensating reactive power in networks for adjustment of voltage H02J3/16
• CPC Class Codes: H02J 3/38 Arrangements for parallely feeding a single network by two or more generators, converters or transformers
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: H02M 1/007 Plural converter units in cascade push-pull DC/DC converters with pre-regulator H02M3/3374; DC-AC converters following a DC-DC stage including a high frequency transformer H02M7/4807; DC-AC converters following a DC-DC conversion stage generating periodically varying voltages H02M7/4826
• CPC Class Codes: H02M 1/0077 Plural converter units whose outputs are connected in series
• CPC Class Codes: H02M 3/1582 Buck-boost converters H02M3/1584 takes precedence
• CPC Class Codes: H02M 7/44 by static converters
• CPC Class Codes: Y02B 70/3225 Demand response systems, e.g. load shedding, peak shaving
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers
• CPC Class Codes: Y04S 20/222 Demand response systems, e.g. load shedding, peak shaving

Abstract

A system and method for combining power from DC power sources. Each power source is coupled to a converter. Each converter converts input power to output power by monitoring and maintaining the input power at a maximum power point. Substantially all input power is converted to the output power, and the controlling is performed by allowing output voltage of the converter to vary. The converters are coupled in series. An inverter is connected in parallel with the series connection of the converters and inverts a DC input to the inverter from the converters into an AC output. The inverter maintains the voltage at the inverter input at a desirable voltage by varying the amount of the series current drawn from the converters. The series current and the output power of the converters, determine the output voltage at each converter.

Claims

1. A method for harvesting power from a distributed power system having a plurality of DC power sources and a plurality of DC power converters, the method comprising:

coupling each of the power sources to a respective DC power converter;

coupling the power converters in series, to thereby form a serial string;

coupling the serial string to an input of an inverter;

fixing voltage level at the input of said inverter to a predetermined constant value, thereby holding the input voltage at a set value thereby forcing current flowing through the serial string to vary according to power provided by the power sources, wherein said fixing is performed by said inverter; and

controlling power output from each power source individually and individually varying the input voltage or current to each respective converter according to a predetermined criterion; and

,

monitoring load on each converter individually and limiting power output from each converter to a preset safe level until predetermined criterion is reached.

2. The method of claim 1, wherein said coupling the serial string to said inverter includes coupling the serial string to a DC/AC inverter adapted for said fixing the input voltage to the inverter.

3. The method of claim 1, wherein said controlling power output includes tracking maximum power point of the power sources, and said individually varying the input voltage or the current is performed by setting the input voltage or current so as to draw maximum power from the power sources.

4. The method of claim 1, further comprising:

individually converting the input voltage and current of each converter to output power at current level dictated by the current flowing through the serial string.

5. The method of claim 1, wherein monitoring load on each converter individually and limiting power output from each converter to a preset safe level until predetermined criterion is reached, comprises limiting power until the load reaches a preset value.

6. The method of claim 1, further comprising monitoring power output of at least one of the power source and DC power converter and directing current to a bypass when the power output exhibits predetermined characteristics.

7. The method of claim 1, further comprising individually operating each power converter to monitor and report power related data, the power related data comprising at least one of:

input current to the converter, input voltage to the converter, temperature of the power source, input power to the converter, and available illumination.

8. In a distributed power system having a DC power source coupled to a load, a method for improving the reliability of components within the load, comprising:

coupling the DC power source to the load, the DC power source comprising a plurality of converters;

maintaining by the load the input voltage to the load at a fixed predetermined constant voltage, thereby holding the input voltage at a set value,

the fixed predetermined voltage being a safe operating voltage for the components within the load;

varying the current input to the load according to the power drawn from the DC power source; and

,

monitoring load on each converter individually and limiting power output from each converter to a preset safe level until predetermined criterion is reached.

9. The method of claim 8, wherein the load includes a DC/AC inverter, and the step of maintaining the input includes maintaining the input voltage of the inverter.

10. The method of claim 9, wherein coupling the DC power source includes coupling solar panels to the converters, and coupling the converters to the inverter.

11. The method of claim 10, further comprising operating said converters to boost the voltage obtained from said solar panels as soon as the solar panels start to output electrical energy.

12. A method for harvesting power from a plurality of solar panels, comprising:

coupling each of the plurality of solar panels to one of a plurality of DC/DC converters;

coupling the plurality of DC/DC converters in series to form a string;

coupling the string to an input of a DC/AC inverter;

operating the DC/AC inverter to maintain a constant voltage at the input;

operating each converter individually to draw maximum power from its respective solar panel and to convert the power to be output at the string by individually varying the input voltage or current to each respective converter according to a predetermined criterion; and

,

monitoring load on each converter individually and limiting power output from each converter to a preset safe level until predetermined condition is reached.

13. The method according to claim 12, wherein operating each converter individually to draw maximum power comprises performing maximum power point tracking individually for each converter.

14. The method according to claim 13, wherein operating each converter individually to convert the power comprises individually selecting power conversion such that the voltages of all of the panels adds to the constant voltage at the input of the inverter.

15. The method according to claim 12, wherein operating the inverter to maintain a constant voltage at the input comprises coupling a shunt regulator across the input of the DC/AC inverter.

16. The method according to claim 12, further comprising coupling at least one additional string the DC/AC inverter, each of the additional strings comprises a plurality of solar panels each coupled to a respective DC/DC converter and each converter being operated to individually perform maximum power point tracking.